Myelin sheath remodelling in regenerated rat sciatic nerve

Brain Res. 1985 Dec 9;358(1-2):163-70. doi: 10.1016/0006-8993(85)90960-6.


Adult rat sciatic nerves were subjected to a crush lesion and allowed to survive during 2 weeks-11 months. Segments of regenerated nerve were removed from exsanguinated animals and subjected to physiological analysis and light microscopic examination of teased fibres. Application of the potassium channel blocking agent 4-aminopyridine (4-AP) to regenerated nerve segments had marked effects on action potential waveform and recovery properties. When applied to normal control nerves 4-AP had minimal effects. Examination of teased preparations from the same nerves revealed the presence of two classes of internodes along regenerated nerve fibres. A majority of conventional regenerated internodes exhibited lengths (L) of at least 150 microns. Maximal L reached about 350 microns after one month survival and 550 microns 10 months later. In the individual nerve the maximal L-values tended to increase with fibre size. Most convential regenerated internodes had L-values of 200-400 microns. In addition, scattered unusually short sheaths, with L-values of 10-150 microns, were found intercalated between conventional internodes. Some intercalated sheaths had a wrinkled irregular configuration and some lacked a light-microscopically distinct myelin layer. We suggest that the occurrence of unusually short and partly distorted sheaths along regenerated fibres reflects a nodal-internodal remodelling in response to longitudinal crowding. These sites might represent foci with aberrant functional properties, possibly accounting for the 4-AP sensitivity of regenerated nerve.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 4-Aminopyridine
  • Action Potentials / drug effects
  • Aminopyridines / pharmacology*
  • Animals
  • Female
  • Ion Channels / physiology
  • Male
  • Myelin Sheath / physiology*
  • Nerve Regeneration*
  • Peripheral Nerves / drug effects*
  • Potassium / metabolism
  • Ranvier's Nodes / physiology
  • Rats
  • Rats, Inbred Strains
  • Sciatic Nerve / physiology


  • Aminopyridines
  • Ion Channels
  • 4-Aminopyridine
  • Potassium